[report-core] disallow define-report with incomplete export info

if exporting is allowed, 'export-types and 'export-thunk must both be
defined.

gnucash/report/report-core.scm

@@ -237,6 +237,7 @@ not found.")))
   (define report-rec (make-report-template))
   (define allowable-fields (record-type-fields <report-template>))
   (define (not-a-field? fld) (not (memq fld allowable-fields)))
+  (define (xor . args) (fold (lambda (a b) (if a (if b #f a) b)) #f args))
 
   (let loop ((args args))
     (match args
@@ -252,6 +253,11 @@ not found.")))
           ((hash-ref *gnc:_report-templates_* report-guid)
            (gui-error (string-append rpterr-dupe report-guid)))
 
+          ;; has export-type but no export-thunk. or vice versa.
+          ((xor (gnc:report-template-export-thunk report-rec)
+                (gnc:report-template-export-types report-rec))
+           (gui-error (format #f "Export needs both thunk and types: ~a" report-guid)))
+
           ;; good: new report definition, store into report-templates hash
           (else
            (hash-set! *gnc:_report-templates_* report-guid report-rec)))))
@@ -836,10 +842,8 @@ not found.")))
     (cond
      ((not export-thunk)
       (stderr-log "Only the following reports have export code:\n")
-      (show-selected-reports (cut gnc:report-template-export-thunk <>)
-                             (current-error-port))
+      (show-selected-reports gnc:report-template-export-thunk (current-error-port))
       (stderr-log "Use -R show to describe report\n"))
-     ((not export-types) (stderr-log "Report ~s has no export-types\n" report))
      ((not (assoc export-type export-types))
       (stderr-log "Export-type disallowed: ~a. Allowed types: ~a\n"
                   export-type (string-join (map car export-types) ", ")))

gnucash/report/test/test-report.scm

@@ -11,6 +11,7 @@
   ;; will create Testing/Temporary/test-asset-performance.log
   (test-check1)
   (test-check-invalid-field)
+  (test-check-incomplete-export)
   (test-check2)
   (test-check3)
   (test-check4)
@@ -31,6 +32,21 @@
     1
     (length (gnc:all-report-template-guids))))
 
+(define (test-check-incomplete-export)
+  ;; it's not legit to define report with ONLY export-thunk or
+  ;; export-types. both must be defined.
+  (gnc:define-report 'version 3
+                     'name "Test Report Template4"
+                     'export-thunk #t
+                     'report-guid "incomplete-export-guid")
+  (gnc:define-report 'version 3
+                     'name "Test Report Template4"
+                     'export-types #t
+                     'report-guid "incomplete-export-guid")
+  (test-equal "report with incomplete export thunk"
+    1
+    (length (gnc:all-report-template-guids))))
+
 (define (test-check-invalid-field)
   (gnc:define-report 'version 3
                      'name "Test Report Template4"